Treatment of minerals



Patented May 25, 1926.

UNITED STATES 1,585,756 PATENT OFFICE.

WALTER O. BOBGHERDT, OF AUSTINVILLE, VIRGINIA, ASSIGNOR TO THE NEW JER-SEY ZINC COMPANY, 01 NEW YORK, IN. Y., A CORPORATION OF NEW JERSEY.

TREATMENT OF MINERALS.

No Drawing.

This invention relates to the treatment of minerals, and has for itsobject the provision of certain improvements for promoting variousmineral treatment operations in which the mineral undergoing treatmentis associated with colloidal constituents in a mineral pulp.

The .mineral treatment operations to which the resent invention isadvantageously applicable embrace a wide field and include suchoperations as aim to segregate a particular kind or class of constituentor constituents of'the mineral, such,

for example, as concentration, classification, dehydration, thickening,filtration, etc.

Throughout this specification, I have used.

the word concentration in a broad sense for describing any processwherein the purpose is the separation of one or more valuable minerals,or of their valuable constituents, from one or more less valuable(usually waste) minerals; or the separation of valuable minerals, or oftheir valuable constituents, from one another, and, therefore, includingnot only mechanical methods of separation, by which the mineralparticles are rearranged in fractional products Without intrinsicalteration, but also such chemical or quasi-chemical methods ofseparation as depend upon amalgamation with mercury, cyanidation,chlorination, distillation, sublimation, oxidation, reduction, solutionin acids, aklalies or other reagents; by which the valuable mineral, or

' its valuable constituent, although changed in form, is separated fromthe other minerals with which it was originally associated, and isrecovered in an alloy, salt, distillate, sublimate, metal, oxide, orchemical compound, etc., in which it exists in greater proportion thanin the or ginal mineral mixture.

While I shall, herein, for the purpose of simplicity, generally use thesingular numbeer in mentioning the valuable minerals, it will beunderstood by those skilled in the art that in some instances more thanone valuable mineral species exists in a given mineral mixture or pulp,and that it may be desired to produce more than one kind of concentrateor product therefrom, as by a combination or succession of concentratingsteps of the same or different kinds, with the result that each suchconcentrate contains, respectively, a greater proportion Applicationfiled December 11, 1922. Serial No. 606,341.

of some one mineral species or of its valu. able constituents than theothers, or than the original mineral mixture or pulp.

Since my invention is applicable to the preparation of many kinds ofmineral mix tures for various mineral treatment operations, such, forexample, as concentration, I Wish to be understood when referring to'mineral pulp as including in this term mixtures of natural orartificial minerals with a liquid, and, therefore, comprehending ores,tailings, middlings, smeltery slags, flue dusts, fumes, furnaceproducts, manu factured materials, foundry or factory sweepings orsimilar debris, coal, coke, sand, gravel, concrete aggregate, rockcrushed for agricultural purposes or for fertilizer manufacture,oil-shale, oil rock, oil-sand, etc, when mixed with a liquid to form apulp.

The word mineral, as herein used, is to be understood as includinginorganic substances of substantially constant chemical compositionoccurring naturally in the crust of the earth; such inorganic butartificial substances analogous in structure and use to naturalminerals, and which, by extension of thought, are in practice classed asminerals, and also such substances found in the earth as are organic inthe sense that they are supposed to owe their origin to the plant oranimal life of past geological ages, but are now classed as mineral. Itwill therefore be understood that I intend to include in the wordmineral not only the well recognized natural minerals, me-

tallic and non-metallic, but also metals, elements, smeltery slags,flue-dusts, foundry or factory sweepmgs or similar dbris, coal, coke,bitumens, petroleum oils, etc.

For the purposes of explanation, the present invention will beparticularly clescribed as applied to the concentration of minerals, andthe understanding of the invention derived from this description willenable those skilled in the art to successfully apply the principles ofthe invention to other mineral treatment operations.

Certain general principles are of universal application in theconcentration of valuable minerals or of their valuable constituentsfrom mixtures. All such mixtures must be prepared for concentration,usually by crushing, grinding, screen sizing or hydraulicclassification, or by one .or more of these steps. By such methods, aconsiderable part of the mineral mixture is reduced within a range ofparticle size which renders it amenable to treatment by one or moreofthe well known processes of concentration. However, it is inevitablethat in so preparing the material, even by the most refined methods ofgraded crushing and classification, a part of the mineral mixture isground so fine that, taken together with the fine particles resultinfrom blasting and other mining and handling operations, it constituteswhat is known in the art as slimes Slimed material is, of course, not ofuniform particle size. In fact, the range of particle size in slime isprobably quite as great as, and may be much greater than, theproportionate range of particle size in the other fractional parts intowhich the mineral mixture is divided. Likewise, the slimed material mayhave approximately the same chemical composition as the originalmaterial or mineral mixture, or it may be that certain of the mineralconstituents in such original material or mineral mixture, by reason ofproperties peculiar to them, or developed in them to a greater degree,may slime to a greater extent, and therefore, be present in the slimesin greater proportion. The fact remains, however, that slimed materialis always present in normally prepared mineral mixtures, and it alwayspresents special problems in handling and treatment. In some specialcases, it is desirable to slime the entire mineral mixture beforeconcentration, but usually that is not desired and it is necessarysimply to apply to the slimed portion of the mixture such specialmethods of concentration as may be found economically available.

A portion, be it large or small, of every sli1ne,,may be characterizedas colloidal, and it is with this colloidal material that I have dealtin the discoveries which form the basis of the present invention.

It is well known that colloids and colloidal slimes, both organic andinorganic, often are present in mineral pulp, and when present inconsiderable amount, may have an unfavorable effect upon theconcentration of such mineral pulp. When considerable amounts ofcolloids or colloidal slimes are thus present, itis usually necessary tooperate in a more dilute pulp. The colloidal matters present in amineral pulp are probably derived for the most part from the gangue ornon-valuable particles of the mineral mixture, although it is notunlikely that valuable mineral particles may also be present in the pulpin the form of colloids. Such colloidal matters may also be introducedwith the milling water which is used to form the mineral pulp, and thissource of colloidal matters may be considerable during periods of heavyrainfall when surface waters containing mud and other suspended matters,and heavily charged with both organic and inorganic colloids, run intothe source from which the milling water is customarily taken.

The colloidal matters may be present as pure colloids, organic orinorganic, or in a state bordering on the so-called coarse suspensions.Throughout this specification and the appended claims, I intend toembrace in the expressions colloids, colloidal slimes and colloidalconstituents both true colloids and those quasi or borderland substanceswhich may not be truly colloidal but partake of the qualities of, orresemble, colloids, and without regard to the sources from which suchcolloidal matters are derived. Thus, for the purposes of the presentinvention, the colloidal constituents may be considered as ranging fromjust above the molecular size upward through the class of so-calledsuspensoids, which, while possibly not true colloids, still, because oftheir relatively large specific surface, exhibit some, if not all, ofthe properties of colloids, and are capable of existing in both the solor gel state, or of being dispersed and coagulated or flocculated anddeflocculated. By a colloidal slime, therefore, I mean a material whichis not necessarily a true colloid, but which exhibits colloidalcharacteristics to a sufficient degree to make it amenable to themanipulation hereinafter described.

It has heretofore been proposed to treat such mineral pulps, containingconsiderable amounts of colloidal slimes, with a coagulating orflocculating agent, in order to neutralize in part the objectionableeffect of such slimes, but the coagulated or flocculated colloidalconstituents remain admixed with the mineral pulp and often seem to formtherewith adsorption compounds or colloidal complexes wherewith themineral particles are entangled or enmeshed and the mineral treatmentoperation prejudiced thereby, as well as, in some instances, by thecoagulating or flocculating agents which remain in solution in themineral pulp.

It has also been heretofore proposed to deflocculate the colloidalconstituents in a mineral pulp preparatory to a mineral treatmentoperation, but here again the deflocculatcd colloidal constituents, aswell as the deflocculating agent when used, remain admixed with themineral pulp during thesubsequent mineral treatment operation? Theremoval of slimes from a mineral pulp containing considerable amounts ofcolloidal slimes has also been heretofore proposed and practiced in whatis generally known as desliming operations, but such operations asusually practiced are incompetent or inadequate to separate thecolloidal from the non-colloidal constituents of the mineral pulp forseveral reasons, among which are the following. The colloidalconstituents of mineral pulps are rarely, if ever,

naturally deflocculated and dispersed to their maximum possible extent.Since aggregated or fiocculated colloid masses actlike solid particlesof greater magnitude, the removal of the partially flocculated colloidalconstituents of a mineral pulp by means of settling processes such asdecantation, or even by washing with water on tables or vanners, isgenerally incomplete and inadequate. The agencies which promote theflocculation of the colloidal'constituents of a mineral pulp also ingeneral seem to promote the adsorption or other form of attachment whichexists between such colloidal constituents and the granular constituentsof the mineral pulp. It follows therefore, that in the ordinary practiceof desliming as by decantation, much of the colloidal matter may remainwith the granular matter of the min-- eral pulp even though, in theeffort to remove it, decantation has been carried to the point wheremuch of the finer granular matter has been decanted off of the mineralmixture. 7

As the result of my investigation, I believe that the injurious actionon the concentraing operation of colloidal matters present in themineral pulp may result from their presence in the mineral pulp, or maybe due to their attachment to, or absorption by, certain minerals of thepulp, or the reagents introduced into the pulp to effect or assistconcentration, or may be due to their combination, chemically, with suchreagents, thus neutralizing them or delaying or inhibiting the actionwhich they are intended to bring about, or may be due to their affectingthe density or viscosity of the pulp, the settling rate of the mineralparticles, the liquid holding capacity of the mineral particles, theentanglement or other form of aggregation of the mineral particles, theconductivity for heat or electricity or the magnetic permeability of themineral mixture, or in other, and less obvious ways. Thus, the colloidalconstituents of the mineral mixture may interfere with its effectivescreen sizing or classification, or with leaching, percolation,filtration, or similar steps employed for concentration or ancillarypurposes, as by filling the pore spaces of certain minerals, or theinterstitial spaces in the mineral mixture, or by clogging andobstructing the pores or crevices of filtering surfaces, or per meablepartitions or diaphragms, or of fluid absorbing or emitting surfaces, orof surfaces designed to have a certain degree of grain or roughness, as,for example, the active surfaces of concentrating devices, such asshaking tables of the VVilfley type, vanners, canvas-plants, buddlcs,amalgamated plates, greased tables, etc. It is my belief that thesecolloidal matters may interfere with concentration operations whetherthey exist in a flocculated (or coagulated) or 1n a deflocculated (ordispersed) condition, but I have found that in general their action isless marked when dispersed or deflocculated.

The present invention in its broad aspect contemplates, as animprovement in the treatment of minerals and more particularly in theconcentration of minerals, and as a preliminary step to the treatment orconcentration operation proper, the removal, in whole or in part, ofcolloidal constituents from the mineral pulp by a flotation treatmentunder conditions permitting the removal by flotation of a part or thewhole of the colloidal constituents while substantially inhibiting theflotation of mineral particles. After the removal of the colloidalconstituents from the mineral pulp by a preliminary flotation treatmentin accordance with the principles of the present invention, the mineralpulp thus freed to the desired extent of the colloidal constituents issubjected to the contemplated mineral treatmentoperation, such, forexample, as a concentration operation.

Thus, according to the present invention, the mineral pulp containingthe colloids or colloidal slimes is subjected to a preliminary flotationtreatment with an appropriate agent or agents, the object of which is toproduce a froth or scum containing part or the whole of the colloids orcolloidal sliines, with a relatively small proportion of the valuablemineral or minerals contained in the pulp, and to separate thiscolloid-bearing froth from the bulk of the pulp, after which theremaining mineral pulp is subjected to the contemplated mineraltreatment operation.

The colloid-bearing froth may itself be further treated for the recoveryof such valuable minerals as it may contain, or it maybe run to waste,but in either event the principal part of the valuable mineral orminerals contained in the pulp is, by the practice of my presentinvention, treated, in the contemplated mineral treatment operation,under conditions which facilitate and expedite such treatment, and, inthe case of a concentration operation, under conditions which enhancethe recovery of valuable minerals.

In some cases the colloid-bearing froth when produced as described maycontain too much valuable mineral to permit of throwing it away. Thismineral may be carried over in part mechanically entangled withfloccules of colloidal material; in part as colloidal complexes ormineral particles with adsorbed colloid coatings which cause them to actlike ganguc or colloidal particles rather than mineral particles; and inpart simply in mechanical suspension in the froth, because of their finesize and the rapid formation of the froth. In order to separate thismineral from the colloid-bearing froth and return it to the mineral pulpwhich has been treated as described for the removal of colloidalmaterial, the froth may be subjected to the action of mechanicalfroth-breakers or of water or air jets to break it down. as is commonlydone in frothflotation plants, and if the froth contains flocculentmaterial, as would ordinarily be the case, a deflocculating agent may beadded, as well as water for dilution of the broken-down froth-pulp tothe desired degree. The kind and amount of deflocculating agent, and theamount of water required may be readily determined for a specificcolloidbearing froth by means of simple tests.

The deflocculated pulp resulting from the foregoing described treatmentmay be then run to settling tanks, which may be of the continuous type,such as Dorr, Allen. or Callow tanks or similar apparatus. orintermittent tanks, such as are commonly -used in the arts and are toowell known to require description. In these tanks sedimentation orsettling may take place, the minerals and coarse gangue particlessettling toward the bottom, and being removed continuously orintermittently. The deflocculated colloidal material, together with muchof the agent used to form the colloid-bearing froth. having a muchslower settling rate, remains in suspension and is continuously orintermittently overflowed to waste. The settled material, containing themineral, may be further treated in a similar manner, if the firsttreatment has not sufliciently removed the colloidal material and thefroth-forming agent, and is then diluted with water as desired andreturned to the body of the pulp which has been treated for the removalof colloids.

In some cases, simple breaking down of the colloid-bearing froth anddilution with water may be sufficient to render possible the separationof the colloidal constituents from the mineral particles and the returnof the latter to the main body of mineral pulp, or in special casesleaching of the minerals with chemical agents, or treatment withsulfidizing agents to make oxidized minerals amenable to flotation, maybe indicated to recover the valuable mineral, but the need for suchtreatments and the procedures to be supplied will in such cases beapparent to those skilled in the art to which this invention pertains.

I have also discovered that while colloids or colloidal slime present-ina mineral pulp often exercise an inhibiting effect upon theconcentration, and especially the concentration by flotation, of thevaluable minerals therein, that this effect generally varies in charge.

strength as respects different minerals; and also, as respects any onemineral, that the inhibitory effect varies approximately in proportionto the amount of colloidal material present; and that the state in whichcolloids exist also has a bearing, the inhibitory effect being generallyless marked when the colloidal constituents are dispersed ordefiocculated.

The removal of the colloids or colloidal slimes by the production andseparation of a colloid-bearing froth may be conducted in one step, asav preliminary operation, when only one valuable mineral is concerned inthe subsequent mineral treatment operation, or it may be conducted intwo or more steps, each removal of colloids or colloidal slimes by aflotation operation being followed by an appropriate mineral treatmentoperation directed particularly towards the recovery or treatment of a.particular valuable mineral. For example, I have found that, for certainpurposes, it is desirable to retain part of the colloidal constituentsin the mineral pulp, and that, when a proper amount of such constituentsis present, it is possible to effect a differential separation orconcentration of a certain valuable mineral species of a mineralmixture, while the separation of another vauable mineral species isretarded or inhibited by the colloids or colloidal slimes remaining inthe mineral pulp; and that, thereafter, by a further removal of a partor all of the remaining colloids or colloidal slimes, in the mannerherein con templated, separation or concentration of the remainingvaluable mineral species can be effected.

As a result of the investigations which I have made, I have been led tobelieve that colloidal adsorption takes place upon metallic surfaces andupon the surfaces of sultides and other minerals, but that the strengthof the adsorption varies considerably, depending upon the character ofthe colloid, its relative concentration, the kind and character ofadsorbing material, and its temperature and condition of electrical 7 Ido not, however, desire to limit myself by any theoretical explanationof the principles underlyin the present invention. Whatever may be thecorrect explanation, of the prejudicial effect of colloids when present,and of the advantages resulting from their removal, the process of thepresent invention involves the separation or removal from the mineralpulp of the colloids by a preliminary flotation operation, and in wholeor in part (whether adsorbed by or otherwise combined or admixed withthe minerals), as a preliminary or preparatory step to a mineraltreatment operation.

gitation of the mineral pulp may in some instances be required in orderproperly to prepare the colloidal constituents for removal from the pulpby froth flotation, and for the proper incorporation of the agentsnecessary for the preparation ofthe pulp for flotation as well as forthe fm'mation of the flotation froth. Such agitation may readily beeffected in apparatus well known in the ore dressing art.

Increase or decrease in temperature may be similarly of assistance inbringing the colloids into a state permitting their, removal byflotation from the mineral pulp. The optimuin temperature in the case ofany particular mixture, for promoting removal by flotation of thecolloidal constituents contained in the mineral mixture, may bedetermined by tests, in which the other factors are held constant andthe temperature varied through a wide range. Where this optimumtemperature is higher than the normal temperature of the mineral pulp,the mineral pulp may be heated to the desired temperature by directheating or by the use of steamheating coils, or by steam blown into thepulp, and where this optimum temperature is lower than the normaltemperature of the mineral pulp, the pulp may be cooled by dilution withcold water, by cooling coils, by cooling towers, etc.

I have found that the necessary distribution through the mass of themineral mixture of the agents used for promoting conditioning orflotation of colloidal constituents can be very conveniently ndeffectively brought, about by adding the agent to the mineral pulp atsome point prior to the admission of the mineral mixture to the ball orpebble mills, or other fine grinding machines. Such machines almostinvariably form a part of the eqiiipment of concentrating plants. By soadding the agent to the mineral mixture ahead of the fine grindingmills, the necessary armixture is secured without inconvenience or addedexpense, and the treatment. of the colloids or colloidal slimes prior tothe removal by flotation from the mineral pulp may take place under themost favorable conditions.

After the colloids or colloidal slimeshave been removed to the desiredextent (that is, in whole or in part depending upon the result desired},the remaining mineral pulp, which may now be in a more concentratedstate with respect to its solid phase, is subjected to the contemplatedmineral treatment operation. To this end, thepulp may be furtherthickened or dried, or it may be dilured, depending upon the nature ofthe subsequent mineral treatment operation, and

then suh ectcdto appropriate treatmentfor securing separation of thevaluable minerals from the waste or less valuable minerals. The removalof the colloids from the mineral mixture often enables the mineralmixture to be treated in a state of greater density, that is, in a moreconcentrated form with respect to its solid phase, with the result thatan increased tonnage of mineral mixture can be handled by a given plant.

The colloidal slimes which are separated from the mineral pulp arecommonly of a character such that they may be run to waste. In case,however, the slimes carry sufficient values, they may be themselvessubjected to a further treatment for the recovery of the valuestherefrom.

'lhe liquid accompanying the removed colloids may be separated andrecovered for reuse. The colloids contained therein may thus becoagulated and settled or filtered out. The liquid separated from thecolloids may be purified, if necessary, to free it from dissolved saltsprejudicial to the mineral treatment operation in which it is to besubsequently used.

If the original mineral mixture contains several valuable ingredientssuch as sulfides, the removal of the colloidal constituents inaccordance with the principles of the present invention may be carriedout in a numberof stages in order to take advantage of the selectiveinhibition of. the colloids or colloidal slimes toward the selection ofcertain of the minerals. For example, in a mixed sulfide mineralmixture, containing sulfides of lead, zinc and iron, which it is desiredto treat by the well known froth flotation process, the mineral mixturemay be treated for the removal of a portion only of the colloidal slimesin the manner hereinbefore described, so that there will be retained inthe mineral pulp sufficient of the colloids to prevent any considerableflotation of the iron and zinc sulfides while permitting the flotationof the lead sulfide, whereby there can be obtained by flotation a leadconcentrate relatively free from zinc and iron. The remaining mineralpulp (tails from the aforementioned flotation operation) may then betreated for the removal of an additional portion of the colloids,whereby flotation of the zinc, or flotation of the zinc and iron, may bereadily effected. Where the zinc is floated without flotation of theiron, a still further removal of the colloids from the remaining mineralpulp may then be effected inorder to permit flotation of the ironsulfide. In carrying out differential flotation of different minerals,advantage may also be taken, in each case, of the well known selectivequalities of certain oils, or other flotation agents, for the variousminerals, such selective qualities supplementing the selectivelyinhibitory action of the colloidal constituents.

It will be seen that the present invention thus involves the separationfrom the mineral pulp, prior to concentration or other mineral treatmentoperation. of colloidal constituents by a preliminary flotationoperation so that the concentration or other mineral treatment-operationis carried out without interference from the colloids, or with suchregulated action of the remaining colloids as is desirable for theparticular object in view, as in case a differential separation ofcertain minerals is desired.

Where the mineral pulp contains, in solution in the liquid thereof,substances which prevent bringing about the desired reliminary conditionof the colloids, or t e flotation thereof, such substances may be inpart or in whole removed, as, for example, by the removal of the liquidfrom the mineral pulp, prior to treatment, or they may be otherwiseneutralized and rendered harmless by methods and a ents which aregenerally known, and can regulated by simple tests. For exam le, anexcessive quantity of magnesimn su fate or of some other electrolyte mayinterfere with the in the mineral proper action 0 s ium silicate as adispers- 1ng agent. Such a condition may be corrected by washing themineral for the removal of soluble salts. Where the mineral ulp is acidor where there is latent acidity, due to the occlusion of sulfurdioxide, an alkaliv may be added to correct the acidity, whereby thesodium silicate is enabled to act in the desired manner.

The principles of the present invention are of special advantage whenapplied to processes of differential concentration, particularlydifferential flotation. Thus by the proper application of theseprinciples it is possible to secure the differential concentration ofcertain mineral species while inhibiting the concentration of othermineral species. This result is brought about by forming acolloid-bearing froth by means of an appropriate agent, employing forthis purpose any of the flotation machines employed for the productionof mineral froths in the ordinary flotation processes, such as theminerals separation, Gallow, J anney, K. & K., etc., but preferably theCallow or other pneumatic machines, (since in these the action. is morereadily controlled), removing this froth from the mineral pulp andeither discarding it or subjecting itto further treatment independent ofthe mineral pulp. After suflicient of the colloidal constituents havebeen removed the remaining pulp is subjected to an appropriateconcentration operation, for example, flotation, and a concentrateobtained composed principall of one of the valuable mineral species 0the pulp. The residual ulp from this concentratin operation is tienagain treated with suitab e agents in a. suitable flotation machine forthe production of a second colloidbearing froth, which is also removedand discarded, or retreated as may be desired; and the remaining pulp isthen subjected a second time to an appropriate concentration operation,such as flotation, for the recovery .maining ore pul of a concentratecomposed principally of a second valuable mineral species, this sequenceof operations being repeated as many times as is necessary for theseparation of each of the valuable mineral species in the originalmineral pulp, singly or in grou s.

As an example of the application of t is aspect of the process of thepresent invention, I will describe the treatment of an ore like thatfound at Austinville, Virginia, which contains the sulfids of lead, zincin a gangue of iron and dolomitic limestone, and in which the colloidsor colloidal sliines are present in such quantities as to seriouslyinterfere with the recovery of the valuable minerals by the usualconcentration processes.

To the finely ground ore, which has been made into an ore pulp byadmixture with water, is added a small amount, for example, one-halfpound per ton of dry ore, of a rosin 'soap in solution in water. Afterthorough mixture the pulp is passed into a Callow flotation cell,through the porous bottom of which air under pressure is admitted infine streams to form minute air bubbles. These air bubbles, with therosin soap and the colloidal, constituents of the ore pulp, form acolloid-bearing froth which rises to the surface of the pul in the cell,and overflows into an approprlately placed launder, which conveys it toa tank for further treatment or to waste. After sulflcient of thecolloidal constituents have thus been removed, the ore pulp is conveyedto an ap propriate concentration apparatus, such for example as anotherflotation cell where a mineral floating agent, as for example,emulsified wood creosote oil, is added and a galena froth is obtained.The residual ore pulp is then mixed with an additional small quantity ofrosin soap, for example, onequarter pound per ton of dry ore, insolution in Water, and passed into another flotation cell, where asecond colloid-bearing froth is formed and removed as before. The orepulp is now passed to another concentration apparatus, such as anotherflotation cell and a small amount of pine oil and crude petroleum oil inemulsion and a small amount of copper sulfate solution are added, and aflotation operation conducted for the formation of a blende froth, whichis removed and further treated as is customary. To the reis then added afurther small amount 0 rosin soap, for example one-quarter pound per tonof dry ore, in solution in water, and the ore pulp is then passed intoanother concentration apparatus, such as another flotation cell wherethe remainder of the colloidal constituents of the ore pulp are removedin the form of colloidbearing froth as before. The ore pulp is then lpof su furic acid, for example, one-half pound referably mixed with-asmall quantity i l l per ton of dry ore, and with emulsified pine oiland crude petroleum oil and passed into a flotation cell where a mineralfroth containing the pyrite is formed and removed, while the finaltailings pulp from the cell is sent to waste.

According to the present invention, the colloidal constituents of theore pulp which are to be removed in whole or in part by the formation ofa colloid-bearing froth, may be in either a flocculated or deflocculatedcondition, the preference being determined by economic considerations,depending upon the kind of valuable mineral or minerals contained in theore, the amount of colloidal matter present, the average fineness of thevaluable minerals,'the tendency or otherwise of the flocculated colloidsto enmesh or entangle valuable mineral, the

soluble contaminants of the mineral pulp,

the degree of dilution of the mineral pulp, the subsequent treatment towhich the colloid-bearing froth and mineral pulp or mineral concentrate,respectively, may be subjected, the tonnage to be treated, the cost ofwater and'agents, etc, In any actual case the natural character of theore and other fixed conditions will determine certain features of theexact method of treatment, while the preference as to other features maybe readily determined by simple tests which will in each case besuggested by the problem itself.

There are several aspects from which the process of the presentinvention must be viewed in order to understand the several means andagents which may be required to effectually carry out the several stepswhich may be necessary in connection with the preparation of a givenmineral mixture for a mineral treatment operation.

It is important to observe that in order to effect the removal ofinhibitory colloidal con- 1 stituents from a mineral pulp they mustgen-. erally also be detached from the granular particles to which byadsorption or otherwise they may be adherent, and to release granularparticles from entanglement with colloid masses such as floccules or-.coagul'es with which they may be enmeshed. 'As previously noted, thecolloidal constituents of mineral ulps are naturally usually flocculentand 1n the practice of the present invention. it

may frequently be necessary or desirable to more completely disperse ordeflocculate such colloidal constituents in order to facilitate theirremoval from the granular particles of the mineral pulp and to releasegranular particles from colloid entanglement.

Since the actual removal of the colloids from the mineral pulp is oftenfacilitated by having them in a flocculent condition at the time of theformation and removal of the colloid-bearing frpth, it follows, thatunder conditions which inhibit any tendency of the colloids to againentangle granular particles or to absorb thereon or fromcolloid-complexes therewith.

Such steps, preparatory to the actual formation and removal from themineral pulp o-f colloids by means of a colloid-selective froth, I groupunder the term colloid-conditioning steps and I will describe themethods and agents which may be used under different conditions so thattheir application and control will be clear to one skilled in the art towhich this invention relates.

In many cases it will be found that the colloidal constituents ofmineral mixtures are in art. at least attached to the valuable minera sof the mixture, forming adsorption films thereon, or colloidalvcomplexes. In such cases it may be necessary to use means and agents toinsure the detachment from the mineral surfaces of the colloidal matter.Such means and agents as will readily be understood are perhaps of thenature of detergents orcleansers, and serve a purpose which is whollydistinct from the production of the colloid-bearing froth, al-

though in some instances the same agents and means may suffice for bothpurposes.

Thus a soap may be used for its detergent action as well as for itsvalue as a colloid-selective frothing agent, and agita tion orregulation of temperature, or both,

may be required to facilitate the detergent action, and may also aid inthe formation of the froth r Sodium silicate is often valuable as anagent for promoting the removal of colloidal matter from granularparticles. It must be used in a neutral or alkaline pulp to give thebest results, and when so used it may act both as a detergent and as adeflocculating agent. Similarly, gum arabic, (acacia) foundry molassesand trisodium phosphate are useful agents for promoting dispersion ordefiocculation and aiding in the removal of colloidal matter fromgranular articles.

When the col oidal matters present in the ore pulp require to beflocculated in order to facilitate their removal from the mineral pulpby the process of the present invention, means and agents may beemployed for that purpose which are well known to those skilled in theart to which this invention relates. Thus various acids, such assulfuric or hydrochloric acid may be used, or alkaline agents, such asthe soluble hydroxides, or salts such as magnesium sulfate, alum,aluminum sulfate, the chlorides etc.

In general, it may be said that the choice of agent or agents to be usedfor conditioning the colloidal constituents of the mineral pulp in orderto facilitate their removal from the latter by means of the formationand removal of a colloid-bearing .t'roth, will be guided by theprinciples of general and colloid chemistry, and in any actual case, dueconsideration being given to the further treatment to which the pulp isto be subjected, the choice of agents will be, made as the result of aseries of tests such as may be made by any one skilled in the art..l'hethcr the agent be chosen for what i have called its detergentaction. or whether it be chosen for the purpose of securing flocculationor deilocculation it mustof coursebe properly selected with reference tothe colloidal properties of the mineral. mixture and in accordance withthe known principles of colloid chemistry so that the desired action maytake place. The nature of the agent will accordingly vary somewhat withdifferent mineral mixtures, becaus the colloidal constituents vary, insome. cases being of a basic character and in others of an acidcharacter, and in some cases being positively charged, and in othercases being negatively charged. The agent may thus be of an acidcharacter, in case the desired conditioning of the colloids may thus bebrought about, or of an alkine character, if the preliminary testsindicate this to be desirable. The agent or agents may themselvespartake of a colloidal character as, for example, silicic acid or sodiumor potassium silicates, or soaps which also display acid or alkalinecharacteristics.

In connection with the removal of colloid films or adsorptions orcoatings from granular particles, or the breaking up of colloidcomplexes or entanglements which affectthe valuable mineral particles ofthe pulp, I have called attention to the importance of preventing orinhibiting the re forming of such films or complexes while the colloidalconstituents are still present in the pulp. In many instances the timefactor necessary for such adverse actions to occur is naturally so longthat the step of formingand removing the colloid-bean iug froth may becarried out before the adverse action has time to take place, (speciallyif the proper conditions for suppressing or delaying such action aredetermined by tests and made elfcctive. In t' l'll fl' cases i havefound that maintaining the mineral pulp in a state of agitation or thatregulating its temperature is sutlicient to maintain the colloids in thedesired state until the separatory step can be taken.

In still other cases I find that it is advisable to employ an agent forthe purpose of forming with the colloidal constituents preferentialcomplexes or adsorption products, thereby preventing them from formingundesired combinations with the minerals of the pulp. Thus I have foundthat in some cases it is advisable to introduce an oil, grease, fat ortar, preferably in an emulsified condition, and that the colloids seemto form therewith combinations which serve to prevent them from againcombining with or adhering to the minerals, and often also facilitatethe collection of the colloidal matters in the colloid-bearing froth. Icall agents used for this purpose gathering agents and I have found thatcrude petroleum oils, fuel oils and some of the fatty acids are oftenuseful for this purpose, as are also, in some cases, certain chemicalprecipitates, such as the hydroxides of alcium, magnesium, aluminum andiron. Sometimes such precipitates can be secured by the skillful use ofone or more substance naturally occurring in solution in the water ofthe mineral pulp. In other cases I have found that the remo'al of thecolloidal constituents may be facilitated by adding to the pulp suchsubstances as finely divided carbon, in the form of powdered coal, cokeor charcoal, or sawdust or similar substances which possess the power ofholding to themselves the colloids which it is the purpose of this ii.-vention to remove from the mineral pulp.

It will be well understood that the agent used for forming the flotationfroth must be such as will be selective for the colloidal constituents,rather than for the valuable mineral which it is desired shall beretained in the pulp. Tests similar to those commonly made to determinethe agents suitable for the froth flotation of valuable minerals, aswill be well. understood by those skilled in the art, will suflice todetermine in a given case which of the various available agents will bebest adapted to the production of the desired colloid-bearing froth.

In the production of colloid-bearing froths, many agents or combinationsof agents are available. One at least of the agents must be such as willbe capable with air or gas bubbles in the pulp of forming a froth orscum which will rise to the surface of the pulp. In the investigation ofthis discovery, I have found many agents, both organic and inorganicwhich are effective. but iheir relative value in the case of any givenore will depend upon a variety of factors. some of wl'iich are mentionedabove, and simple tests will in any event determine the most suitableagent or agents. I have found in practice that pine and hard wood taroils, rosin oils, high temperature distillates, or in general oils witha high pitch content, make excellent agents for the formation ofcolloid-bearing froths substantially non-selective for the valuableminerals present in the ore pulp. Soaps of various kinds, and especiallyrosin soaps, are excellent with some ores, and generally give abundantfroths, and oleic acid and oleic soaps are often useful. In many casesthe same oil or oils which are used for the production of a mineralfroth with a given ore will yield an excellent colloid-bearing,substantially non-mineral-selective froth for the purpose of the presentinvention, if simply used in excess over what would be practicable forthe formation of a mineral bearing froth. In such cases as the last avery simple operation may result, as it is well known that, when afrothing agent is added to water and a froth is produced, that thegreater part of the frothing agent concentrates in the froth, and isconsequently eliminated with it from the pulp, from which it resultsthat after the colloidal constituents of a pulp have been removed bymeans of a colloid-bearing froth, that the remaining frothing agent inthe ore pulp may be sufficient for the production of a mineral frothaccording to the usual processes.

In such cases as it is necessary to use for the formation of thecolloid-bearing froth an agent or agents whose residual presence in theore would be objectionable in the subsequent mineral treatmentoperation, it is possible to neutralize such residual portions bycommonly understood chemical means, and I have found, as a result of myinvestigations, that when an ore pulp has been approximately freed ofits colloidal constituents, that mineral concentration, particularlyflotation, can be conducted satisfactorily in the presence of muchlarger quantities of soluble impurities than would otherwise bepracticable.

In my copending application, Serial No. 584,572, filed August 26, 1922,(the same being a continuation in part of my application, Serial No.283,628, filed March 19, 1919) for improvements in the treatment ofminerals, I have described and claimed, as a preliminary step in thetreatment of minerals and more particularly in the concentration ofminerals, the removal, in whole or in part, of colloidal constituents ina dispersed or deflocculated condition from a mineral mixture or pulp.In the aforementioned application, I have particularly described thetreatment of a mineral pulp for dispersing or deflocculating thecolloidal constituents therein, as, for example, by the addition of anappropriate dispersing or deflocculating agent to the mineral pulp, andthe removal of the dispersed or deflocculated colloidal constituents toa desired extent from the mineral pulp in any appropriate manner, as,for example, by sedimenation of the mineral particles and separation ofthe dispersed or deflocculated colloidal constituents by decantation.The method of my present invention for the removal from a mineral pulpof colloidal constituents by a flotation treatment and the formation ofa colloid-bearing froth may advantageously be employed in conjunctionwith the method of my aforementioned application for removing colloidalconstituents'in a dispersed or deflocculated condition from a mineralpulp. For example, the combination of these two methods ofcolloid-removal may be of particular advantage in connection withdifferential concentration of minerals. Thus, in certain cases, it willbe found of advantage to initially apply the colloid-removing method ofmy aforementioned application so as to make possible the concentrationof one valuable mineral species in the mineral mixture or pulp whileinhibiting the concentration of other valuable mineral species therein,and after the contemplated concentration operation in which the onevaluable mineral species is removed to the desired extent from themineral pulp or mixture, then preparing the residual mineral pulp by thecolloid-removing method of my present invention for the concentration ofother valuable mineral species remaining therein. In other cases, itwill be found more advantageous to initially apply the colloid-removingmethod of my present invention, and subsequently the colloid-removingmethod of my aforementioned application. p

In the case of the ore mined at Austinville, Virginia, I find that ifthe colloids are removed by the method of my aforementioned applicationto the oint where a good galena forth can be pro need from the remainingpulp by a flotation operation, that it is often difficult to makethegalena froth pick up the coarse/galena particles without carrying overan undue proportion of blende. This results from the fact that when partof the colloid is removed the differentiation between that part of thegalena which is most difiicult to float (that is the coarse galenaparticles) and that part of the blende which is easiest to float (thatis the fine blende particles) is not sufficiently marked to give a sharpor clean-cut separation. In such cases, I find that if instead of usingthe method of my aforementioned application I use the method of mypresent application employing a soap as for example rosin soap, to makea very heavy over-stabilized colloidbearing froth and also employ somewood creosote, as a galena-selective agent, that I can carry into thecolloid-bearing froth, not only so much of the colloid that the blendecan thereafter readily be floated fro'm the remaining pulp, but I canalso carry into this collold-bearing froth, by means of thegalena-selective wood creosote, practically all of the galena containedin the pulp. I can then take this over-stabilized galenabearin froth,break it down, deflocculate the col oidal constituents therein to thedesired extent with sodium silicate and decant off the deflocculatedcolloidal matter together with the bulk of the water and most of thesoap and creosote, leaving as a sediment, the galena, accompanied by alittle blende and a certain amount of gangue. The sediment thus producedcan readily be treated by flotation to separate a high grade galenaconcentrate from the gangue.

The colloidal-bearing froth produced in accordance with the principlesof m present invention may thus intentiona ly or otherwise contain suchan amount of valuable minerals as to render economical the subsequenttreatment of the colloid-bearing froth for the recover therefrom ofthese valuable minerals. he minerals thus recovered from thecolloid-bearing froth may be returned to the remaining ore pulp fromwhich the colloids were removed, or may be separately treated for theconcentration of the values therein. Where, as described in the recedingara-graph, the colloid-bearin 0th is de iberately made to include a vauable mineral species, it will generally be more advantageous toseparately treat this colloid-bearing froth as, for example, b themethod of my aforementioned app ication, for the removal of the colloidstherefrom, and then treat the remaining mineral matter for the recoveryof the valuable mineral s ecies.

It will also understood that when the process of the present inventionis applied. to the concentration of several mineral species from a'single mineral pulp, as, for example, by the differential frothflotation process, that it may sometimes advantageously be combined withwell known differential flotation processes which cle end for theireffectiveness in permitting t e flota tion of one mineral species, whileinhibiting that of another, upon the use of certain chemical agents,such as sulfur dioxide, acids, permanganates, or other salts. When soused, these agents must of course be such as will either enhance, or atleast not pre vent, the "colloid-conditioning, gathering andcolloid-removing steps contemplated by the present invention, and ineach actual case tests must be conducted on the given mineral mixture todetermine the se quence of operations and the agents which may best beemployed to secure the desired results.

The present invention is applicable to different concentration processesand with various means or reagents or agents which are used to eflect orfacilitate concentration, Thus, the amalgamation of certain ores of goldand silver has proved difficult or impracticable because of the presenceof oil, grease, tallow, talc, serpentine, graphite, clay and othersubstances. The saprolitic ore of the Appalachian gold belt is anexample. lVhen substances of colloidal character, such as thosementioned and many others, are present in the ore pulp, they seem toattach themselves to or to combine with the precious metal or theamalgam, or to both. The result may be hard amalgam or sickening orfiouring of the mercury, resulting in failure of the amalgam to catchand retain the precious metal. Simple tests will serve to show whetherloss of precious metal values is indeed due, in any given instance, tothe presence of such substances, and equally simple tests, which may beperformed by anyone skilled in the art to which this invention relates,will develop what reagents are required to produce or maintain theoptimum condition of the injuries colloidal constituents, so that theymay be removed from the ore pulp to the desired extent by a flotationtreatment be for the latter is subjected to amalgamation treatment forthe recovery, in concentrated form, of its precious metal content.

In cyanidation, chlorination, acid or alkali leachin or similarprocesses of concentration of mineral mixtures, the presence ofcolloidal constituents may be objectionablein various ways, as byabsorption or other form of attachment of the colloidal constituents bythe valuable mineral particles, or by adsorption by the colloidalconstituents of the reagents used in or reliminarily to the process ofconcentration, or by neutralization or other form of chemicalcombination of the added reagents with the colloidal constituents (theextremely fine state of division of the latteroften servin to permitreactions which would be eit er non-existent or too slow to betroublesome between such reagents and coarser particles having chemicalcomposition similar to that of the colloidal constituents); or bymechanical interference with the porosity or permeability of the mineralmixture, or of parts of the necessary apparatus, thus injuriouslyaffecting the percolation of solutions, the functioning of porous septaor diaphragms, etc.

In such chemical or quasi-chemical methods of concentration, it iscommon to preliminarily separate the slimed from the granular portion ofthe mineral pulp and treat these portions separately by processesdepending upon the same or different princi les. From such a procedure,the method 0 the resent invention is readily distinguishab e, since itis not my purpose to separate the slime as a whole from the granularportion of the mineral pulp, but on the contrary, the present inventioninvolves the separation of the colloidal constituents in a flotationfroth from the slime and granu lar material. Thus, the application ofthe invention in a given instance may, by the removal of the colloidalconstituents, render unnecessary any separation of the slimes from thesands, and the thus removed colloidal matter may be of such character asnot to require or deserve treatment, or it may be so slight in quantitycompared with the slime as a whole as to require smaller apparatus or aless quantity of reagents.

The adsorption or other form of attachment of the colloidal constituentsof a mineral mixture to the granular particles thereof is a matter ofcommon knowledge. Regardless of whether the actual concentration of thevaluable mineral is effected from a pulp or from a dry mineral mixture,the pre iminary removal of the colloidal constituents in accordance withthe principles of the present invention generally leads to improvedresults. Thus, the colloidal mat ter, if valuable, may be saved frombeing lost with the granular waste minerals to which it is in partadherent, whilst, if valueless, it may thus be prevented from adheringto and contaminating the concentrate particles. These considerations areof moment in the preparation of a mineral mixture for dry electrostaticor magnetic concentration. Similarly, in wet magnetic concentration, thepresence of colloidal matter, particularly when fiocculated, mayinjuriously affect the freedom with which the magnetic particles may beseparated from the remainder of the pulp, the slightest entanglement ofthe magnetic particles being the cause of inferior concentration.

In the process of jigging mineral pulps, it might be supposed, sincerelatively coarse particles are dealt with, that colloidal constituentsmight have unimportant influence. On the contrary, it is known thatslimes, when present in the ore being jigged, may seriously interferewith the operation, because they segregate in the places where the.agitation is not so severe, or where there are eddy-currents, and formhard spots, or they may render the jig-bed dense and gummy. It is,indeed, sometimes the case that the slimes form spots or rims in thejig-bed, through which gangue finds its way into the jig-tank or hutch.I have discovered that this well known and objectionable action ofslimes in jigging may be overcome if the colloidal constituents of thepulp are removed therefrom, in the manner set forth in thisspecification, before jigging, and it seems probable that the reason forthis improvement in results is to be found in the fact that when thecolloidal constituents are absent the interstitial spaces in the slimesare filled with water, having low viscosity, instead of with acolloid-water complex having high viscosity, and the mobility of thejig-bed is thereby insured, pe mitting it to function, as desired, inaccordance with the laws of hindered settling. The effect of the removalof colloidal constituents is in eneral quite marked. In a specific caseI ave found that in jigging on a Hancock jig a pulp consistmg of thesulfids of lead, 'zinc and iron in a dolomite gangue, all particles ofwhich were through a screen with one-quarter inch square openings, thatit was necessary to remove all material finer than fourteen-mesh Tylerstandard, in order to permit satisfactory jigging; unless the colloidalconstituents were preliminarily removed from the pulp. When this wasdone, it was no longer necessary to screen or hydraulically classify thepulp, but the entire pulp, minus the removed colloidal constituents,could be jigged with satisfactory results. Preliminary removal of thecolloidal constituents frequently permits also of greater economy in theuse of water and allows the jig water to be used over and over withoutbeing clarified.

I have previously alluded to the beneficial results which follow thewithdrawal of colloidal constituents from mineral-pulp which is to betreated on shaking or bumping tables, vanners, bateas, slime-tables,buddles, canvas, carpet, or blanket-plants, etc. In all such devices itis of reat importance that the mobility of the puIp-mass be insured, inorder to permit of the requisite stratification of minerals, graded bydensity, size and shape, and that the pulp receiving surface of thedevice he maintained in its original grained, pitted or otherwiseuniformlyroughened condition. If the interstitial spaces of the pulp arefilled with colloidal constituents the heavy minerals cannot readilysettle to the lowest stratum and the lightest minerals cannot readilyseparate at the top and wash away. If the minute pits or depressions ofthe linoleum, wood, concrete, rubber, metal, cloth, or other material ofwhich the acting surface of the device is composed, become filled withcolloidal matter, the effect is the same as though the tabletop werelubricated or made of perfectly smooth and frictionless material. Undersuch conditions the forward-driving etl'ect of the table-top is lost (indevices like the VVilfley table where this action is a factor),or thedesired conditions of particle equilibrium are disturbed, so thatcertain particles continue to slip under conditions in which they shouldcome to, andcontinue at, rest.

The effects of the colloidal constituents of mineral pulps ininterfering with classification of minerals by screening and hydraulicclassification have been recognized. In screening, the colloidal matter,particularl if flocculated, tends to remain in part witi the coarseproduct, clogs the screen openings and entangles fine particles. Inhydraulic classification, both according to free-settling andhinderedsettling principles, the presence of colloidal matter isobjectionable. As previously stated, the colloidal constituents tend toenvelope fine particles, adhere to course grains, and to hold excesswater in the settled mass, by Virtue both of their intrinsicwater-holding ability and by the wider spacing of particles whichresults from their presence. The effect of the colloidal constituents inaffecting the density and viscosity of the liquid of the pulp, has beenreferred to. In devices like classifiers, jigs, settling tanks, kieves,etc, in which the princi les of free or hindered-settling classi cationare usefully employed, the presence of the colloidal constituents of themineral pump may be, and often is, harmful. Their adverse influence maybe overcome by removing them from the pulp to the degree desired, inaccordance with the prin-' ciples and methods set forth in thisspecification.

I claim:

1. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents, which comprises subjecting themineral pulp to a colloid-selective froth-flotation operation adapted toremove from the mineral pulp a substantial amount of said colloidalconstituents, and thereafter subjecting the remaining mineral pulp to aseparative treatment other than flotation in which such colloidalconstituents as have been removed therefrom would if present exert adeleterious effect.

2. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents, which comprises subjecting themineral pulp to a froth-flotation operation adapted to remove from themineral pulp a substantial amount of said colloidal constituentstogether with some of the valuable mineral constituents in the pulp,treating the constituents so removed from the mineral pulp to recovervaluable mineral constituents therefrom, returning the valuable mineralconstituents-so recovered to the remaining mineral pulp, and thereaftersubjecting the remaining mineral pulp to a separate treatment in whichsuch colloidal constituents as have been removed therefrom would ifpresent exert a deleterious effect.

3. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents, which comprises subjecting themineral pulp to a frothflotation operation ada ted to remove from themineral pulp a su stantial amount of said colloidal constituentstogether with some of the valuable mineral constituents in the pulp,treating the constituents so removed from the mineral pulp to recovervaluable mineral constituents therefrom, and thereafter subjecting theremainin mineral pulp to a separate treatment in w ich such colloidalconstituents as have been removed therefrom would if present exert adeleterious effect.

- 4. The. method of improving the treatn'ient of minerals associated ina mineral pulp with colloidal constituents, which comprises subjectingthe mineral pulp to a froth-flotation operation adapted to remove fromthe mineral pulp a substantial amount of said colloidal constituents,said froth-flotation operation being preceded by appropriateconditioning of the mineral pulp for promoting the removal therefrom ofcolloidal constituents by froth-flotation, and thereafter subjecting theremaining mineral pulp to a separative treatment other than flotation inwhich such colloidal constituents as have been removed therefrom wouldif present exert a deleterious eflect.

5. The method of improving the treatment of minerals assoclated in amineral pulp with colloidal constituents, which comprises subjecting themineral pulp to a froth-flotation operation adapted to remove from themineral pulp a substantial amount of said colloidal constituents, saidfrothflotation operation being preceded by the step of subjecting themineral pulp to the action of a detergent agent for promoting thedetachment of colloidal constituents from mineral particles in the pulp,and thereafter subjecting the remaining mineral pulp to a separativetreatment in which such colloidal constituents as have been removedtherefrom would if present exert a deleterious effect.

6. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents, which com rises subjecting themineral pulp to a frot -flotation operation adapted to remove from themineral pulp a substantial amount of said colloidal constituents, saidfrothflotation operation being preceded by the step of appropriatelyconditioning the mineral pulp for promoting the removal therefrom byfroth-flotation of the colloidal constituents by adding to the mineralpulp an appropriate gathering agent, and thereafter subjecting theremaining mineral pulp to a separative treatment other than flotation inwhich such colloidal constituents as have been removed therefrom wouldif present exert a deleterious effect.

7. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents, which comprises subjecting themineral pulp to a froth-flotation operation adapted to produce a frothcontaining a substantial amount of said colloidal constituents togetherwith some of the valuable mineral constituents in the pulp, treating thefroth produced by the foregoing froth-flotation operation to promotedispersion or deflocculation of the colloidal constituents thereof, andremoving the dispersed or deflocculated Colloidal constituents from thegranular material contained in the froth.

8. The method of improving the treat ment of minerals associated in amineral pulp with colloidal constituents, which comprises subjecting themineral pulp to a froth-flotation operation adapted to remove from themineral pulp a substantial amount of said colloidal constituents,thereafter subjecting the remaining mineral 'pulp to a separativetreatment in which such colloidal constituents as have been removedthere from would if present exert a deleterious effect, removing fromthe now remaining mineral pulp a further amount of colloidalconstituents therein, and thereafter subjecting the remaining mineralulp to a further separative treatment in which such colloidalconstituents as have been removed therefrom would if present exert adeleterious effect.

9. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents, which comprises subjecting themineral pulp to a froth-flotation operation adapted to remove from themineral pulp a substantial amount of said colloidal constituents, saidfrothflotation operation being preceded by the step f agitating andregulating the temperature of the mineral pulp in the presence of acolloid-conditioning agent for appropriately conditioning the pulp forpromoting the removal therefrom by froth-flotation of coil .dalconstituents, and thereafter subjecting the remainin mineral ulp to aseparative treatment 0t er than otation in which such colloidalconstituents as have been removed therefrom would if present exert adeleterious effect.

10. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents, WhlCll comprises subjectingthe mineral pulp to a froth-flotation o ration adapted to remove fromthe minera pulp a substantial amount of said colloidal constituents,said frothflotation operation being preceded by the step of agitatin themineral pulp in the presence of a col oid-conditioning agent forapropriately conditioning the pulp for promoting the removal therefromby froth-flotation of colloidal constituents, and thereafter subjectingthe remaining mineral ulp to a separative treatment other than otationin which such colloidal constituents as have been removed therefromwould if present exert a deleterious effect.

11. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents, which comprises subjecting themineral pulp to a froth-flotation operation adapted to remove from themineral pulp a substantial amount of said colloidal constituents, saidfrothflotation operation being preceded by the step of regulating thetemperature of the mineral pulp in the presence of a colloidconditioningagent for appropriately conditioning the pulp for promoting the removaltherefrom by froth-flotation of colloidal constituents, and thereaftersubjecting the remaining mineral ulp to a separative treatment in whichsuc colloidal constitue'nts as have been removed therefrom would ifpresent exert a deleterious effect.

12. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents, which comprises subjectin themineral pulp to a frothflotation operation adapted to remove from themineral pulp a' substantial amount of said colloidal constituents, saidfroth-flotation operation being preceded by the ste of treating themineral pulp with a colloi conditioning agent for promoting the removaltherefrom by froth-flotation of colloidal constituents, and thereaftersubjecting the remaining mineral ulp to a separative treatment otherthan otation in which such colloidal constituents as have been removedtherefrom would if present exert a deleterious effect.

13. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents, which comprises subjecting themineral pulp to a frothotation operation adapted to remove from themineral pulp a substantial amount of said colloidal constituents, saidfroth-flotation operation being preceded by the step of heatin themineral pulp in the presence of a colloid-conditioning agent forromoting the removal therefrom by frothotation of colloidalconstituents, and thereafter subjecting the remaining mineral ulp aseparative treatment in which suc colloidal constituents as have beenremoved therefrom would if present exert a deleterious effeet.

14. The method of improving the treatment of minerals associated in a.mineral pulp with colloidal constituents, which comprises removing apart of the colloidal constituents from the mineral pulp, thereaftersubjecting the remaining mineral pulp a separative treatment in whichsuch co loidal constituents as have been removed therefrom would ifpresent exert a deleterious effect, subjecting the now remammg more pulpto a froth-flotation operation adapted to remove from the mineral pulp asubstan tial amount of the colloidal constituents therein, andthereafter subjecting the remaining mineral pulp'to a further separativetreatment in which such colloidal constituents as have been removedtherefrom would if present exert a deleterious efiect.

15. The method of improving the treatment of minerals associated in amineral pulp with colloidal constituents. which comprises subjecting themineral pulp to a frothfiotation operation adapted to remove from themineral pulp a substantial amount of said colloidal constituents,thereafter subjecting the remaining mineral pulp to a separativetreatment in which such colloidal constituents as have been removedtherefrom would if present exert a deleterious efiect, adding to the nowremaining mineral pulp a dispersing or deflocculating agent forprpmoting dispersion or deflocculation of the colloidal constituentsremaining therein, removing the dispersed or deflocculated colloidalconstituents to the desired extent from said remaining mineral pulp, andthereafter subjecting the remaining mineral pulp to a further separativetreatment in which such colloidal constituents as have been removedtherefrom would if present exert a deleterious efiect. v

16. The method of improving the concentration on shaking tables ofminerals assoclated in a mineral pulp with colloidal constituents, whichcomprises subjecting the mineral pulp to a colloid-selectivefrothflotation operation adapted to remove from the mineral pulp asubstantial amount of sald colloidal constituents, and thereaftersubjecting the remaining mineral pulp to concentration on a shakingtable in which such colloidal constituents as have been removedtherefrom would'if present exert a deleterious effect.

17. The method of improving the concentration on shaking tables ofminerals asso ciated in a mineral pulp with colloidal constituents,which comprises subjecting the mineral pulp to a colloid-selectivefroth-flotation operation adapted to remove from the mineral pulp asubstantial amount of said colloidal constituents. said froth-flotationoperation being preceded bv the step of appropriately conditioning themineral pulp for promoting the removal therefrom of col loidalconstituents by froth-flotation and thereafter subjecting the remainingmineral pulp to concentration on a shaking'table in which such colloidalconstituents as have been removed from the pulp would if present exert adeleterious effect.

18. The method of improving the treatment of minerals associated withcolloidal constituents in a mineral pulp, which comprises removing apart of the colloidal constituents from the mineral pulp by acolloidselective flotation operation. subjecting the mineral pulp thusfreed of the removed colloidal constituents to a mineral treatmentoperation, adding to the remaining mineral pulp a dispersing ordeflocculating agent for promoting dispersion or deflocculation of thecolloidal constituents remaining therein, removing the dispersed ordeflocculated colloidal constituents to the desired extent from saidremaining mineral pulp, and thereafter subjecting such remaining mineralpulp thus freed of the removed colloidal constitugnts to a furthermineral treatment operaion.

In testimony whereof I aflix my signature.

WALTER 0. BORCHERDT.

